Electrical apparatus



Nov. 14, 1961 P. NARBUT ELECTRICAL APPARATUS Filed May 16. 1960 3 Sheets-Sheet 1 Fig.|.

.WITNESSES 94 INVENTOR Poul Norbuf Nov. 14, 1961 P. NARBUT 3,009,124

ELECTRICAL APPARATUS P. NARBUT ELECTRICAL APPARATUS Nov. 14, 1961 5 Sheets-Sheet 3 Filed May 16. 1960.

Fig.3.

of certain types of liquid coolants.

United States Patent M 3,009,124 ELECTRICAL APPARATUS Paul Narbut, Hickory Township, Mercer County, Pa., as-

This invention relates to electrical apparatus, and more particularly to electrical apparatus utilizing vaporization of a liquid dielectric to dissipate the heat developed during operation of the apparatus and also utilizing the vapors of the liquid dielectric as an insulating medium,

In U.S. Patent No. 2,561,738 which issued on application of C. P. Hill and is assigned to the same assi-gnee as the present application, there is disclosed an enclosed electrical apparatus employing a relatively small amount of a liquid coolant which is sprayed or applied over the electrical windings of the apparatus to cool them by evaporation of the liquid cool-ant, the evolved vapors constituting a part of an electrically insulating gas mixture which also includes a substantially non-condensable gas, such as sulfur hexafluoride. In certain applications, electrical apparatus of the latter type is provided with associated circuit interrupting or switching means, such as tapchanging equipment, which is disposed in an auxiliary housing or compartment that is closely connected to or mounted on the casing or tank of the associated electrical apparatus. A problem arises where the circuit interrupting means employs certain substantially non-condensable gases having suitable preferred electronegative properties, such as sulfur hexafluoride, to aid in arc extinction during the operation of said circuit interrupting means as disclosed in U.S. Patent No. 2,757,261, which issued on an application of H. I. Lingal et -al., and is assigned to the same assignee as the present application. The problem is to prevent the are products which result during the operation of the circuit interrupting means of the latter type from entering the casing of the associated electrical apparatus and contaminating or detracting from the elfectiveness of the insulating gas disposed therein, particularly where the circuit interrupting means employs sulfur hexafluoride. One means of overcoming the latter problem is to provide a gastight or hermetic separation or partition between the casing of an electrical apparatus and its associated auxiliary compartment in which is disposed the circuit interrupting means. The latter solution, however, may be very difiicult where the casing and the auxiliary compartment are normally separated only by a partition or bartier of insulating material which has a relative degree of permeability to the diffusion or penetration of the vapors It is, therefore, desirable to provide an electrical apparatus of the type described including a main casing and an auxiliary compartment or housing having a circuit interrupting means disposed therein in which the separation between the casing and the auxiliary compartment need not be gastight and in which the are products which result during the operation of said circuit interrupting means are prevented from entering the casing of the associated electrical apparatus.

It is an object of this invention to provide a new and improved electrical apparatus of the enclosed type employing the vaporization of a liquid coolant to dissipate the heat developed therein and including circuit interrupting means embodying certain types of non-condensable gases as the arc interrupting medium.

Another object of this invention is to provide means for preventing the are products of a circuit interrupting means employing certain types of non-condensable gases, such as sulfur hexafiuoride, as an arc interrupting medium from entering the casing of an associated electrical ap- 3,009,124 Patented Nov. 14, 1961 paratus which is cooled mainly by the evaporation of a liquid coolant.

Other objects of the invention will, in part, be obvious and will, in part, appear hereinafter.

For a fuller understanding of the nature and objects of this invention, reference should be had to the following detailed description taken in connection with the accompanying drawing, in which:

FIGURE 1 is a diagrammatic view of a transformer constructed in accordance with this invention;

FIG. 2 is a diagrammatic view of a transformer illustrating a second embodiment of this invention;

FIG. 3 is a schematic diagram of the transformer shown in FIG. 1 illustrating the type of electrical apparatus in which the invention may be employed; and,

FIG. 4 is a diagrammatic view of a transformer illustrating a third embodiment of the invention.

In accordance with this invention, an enclosed electrical apparatus including circuit interrupting or switching means is provided that combines the advantages of the liquid dielectrical filled type apparatus in many respects and also the advantages of the gas-filled types of electrical equipment with few or none of the disadvantages of either type of apparatus, and with several unique advantages of its own. More specifically, the operating electrical elements or windings of the apparatus are cooled by flowing, spraying or otherwise distributing over the surface to be cooled in layers, streams or films of certain liquid fluorinated organic compounds having a boiling point of between 50 C. and 225 C. at atmospheric pressure. The fluorinated organic compound or a mixture of two or more compounds cools the electrical elements or conductors of the apparatus mainly by its evaporation. The fiuorinated organic compound vapors so evolved flow to the enclosing main casing of the apparatus in which the elements are disposed and condense on contact at a relatively cool wall of the casing or they may be condensed in a radiator or by other suitable means. The condensed liquid compound and any portion of it that did not evaporate when sprayed or flowed over the electrical windings or conductors of the apparatus are collected and reflowed or resprayed. A relatively small amount of liquid fluorinated organic compound has been found to be sufiicient for effective cooling of a particular electrical apparatus,

In order to provide the necessary insulation during the operation of electrical apparatus, an insulating gas is provided in the main casing of the electrical apparat-us which is a mixture of a relatively inert, noncondensable gas and the vapors of the fluorinated organic compound. The non-condensable gas is necessary to insure adequate initial insulation. When the apparatus is cold or inoperative, the non-condensable gas constitutes the predominant volumetric proportion of the insulating gas in the main casing of the apparatus and the vapors of the fluorinated compound constitute the minor component. During the operation of the apparatus, the temperature will increase with the applied load and the composition of the atmosphere surrounding the windings or conductors of the apparatus will comprise a greater proportion of the vapors of the fluorinated compound. Mixtures of a non-condensable gas, such as sulfur hexafluoride or nitrogen, and the vapors of the fluorinated compounds are not as eficient in conveying heat from the windings to the casing walls or radiator of an electrical apparatus, since the non-condensable gas impedes the flow of the evolved vapors to the radiator or casing walls and impairs its condensation. In order, therefore, to obtain the most efficient dissipation of the heat developed in the operating elements or windings of an enclosed apparatus, the non-condensable gas in the main casing may be segregated from the vapors of the fluorinated compound during operation so that substantially only the vapors of the fluorinated compound are present in the portion of the casing adjacent to the operating elements or windings.

The circuit interrupting or switching means which is included with or associated with an electrical apparatus as disclosed is disposed in an auxiliary compartment or housing which is closely connected to or mounted on the main casing of the electrical apparatus. In order to provide a more effective are extinguishing medium for the circuit interrupting means, the auxiliary compartment is substantially filled with a suitable substantially non-condensable gas having preferred electronegative properties, such as sulfur hexafluoride, as disclosed in the Lingal patent previously mentioned. In order to eliminate the need for a gastight separation or partition between the auxiliary compartment which houses the circuit interrupting means and the associated main casing of the electrical apparatus, a gas passageway is provided between the auxiliary compartment and the associated main casing which includes means for absorbing or removing the arc products which result during the operation of the circuit interrupting means. Since the auxiliary compartment or housing and the associated main casing are therefore in gaseous communication with one another, the difference in pressure between the insulating gas and the main casing and the pressure of the non-condensable gas in the auxiliary compartment which also serves as arc extinguishing medium is substantially negligible. Since the auxiliary compartment normally operates at a lower temperature than the associated main casing, there will be normally a higher concentration of the non-condensable gas in said compartment than in said main casing even though the pressures in said compartment and casing are substantially the same.

Different vaporizable liquid coolants are known to those skilled in the art and can be employed in practicing this invention. In practice, it is generally preferred to utilize the vaporizable liquid coolants disclosed in the Hill Patent 2,561,738 and in copending application Serial No. 744,18 filed June 24, 1958 by A. I. Maslin and myself and issued November 22, 1960 as US. Patent 2,961,476 which are both assigned to the same assignee as the present application. The vaporizable liquid coolant may comprise the liquid fluorinated organic compounds selected from the group consisting of hydrocarbons, hydrocarbon ethers and tertiary hydrocarbon amines in which at least half the hydrogen atoms have been substituted by at least one halogen selected from the group consisting of chlorine and fluorine, and of which at least half of the halogen is fluorine. The hydrocarbons and the hydrocarbon groups attached to oxygen or nitrogen atoms may be aliphatic, aromatic, cycloaliphatic and alkaryl. Liquid pertluorocarbons, perfiuorocarbon ethers and perfiuorocarbon tertiary amines boiling between 50 C. and 225 C. have outstanding properties. Perhalocarbon compounds composed of only carbon and a halogen selected from at least one of the group consisting of chlorine and fluorine, of which fluorine comprises at least half the halogen atoms are excellent liquid coolants for the purpose of this invention.

The vapors of the fluorinated organic compound referred to hereinbefore have outstanding electrical insulating properties. They are superior to practically all other gases in such electrical insulating characteristics as breakdown strength, dielectric strength, power factor and resistance to formation of corona under similar conditions of temperature and pressure. These compounds are outstanding in their stability to chemical and thermal breat down, being surpassed only by the permanent gases. The fluorinated compounds in the liquid state exert negligible, if any, solvent or deteriorating action on ordinary insulating materials and varnishes employed in the preparation of conventional electrical elements such as windings, cores, and coils.

As examples of specific fluorinated organic compounds which may be utilized in practicing this invention either alone or in mixtures, reference may be had to the following list of fluorinated organic compounds:

Boiling point, C.

Perfluorophenanthrane 20S Perfiuorodibutyl ether Perfluorotriethyl amine 71 Perfiuorotributyl amine 178 Perfluorodimethylcyclohexane 101 Perfiuoromethylcyclohexane 76 Perfluoro-n-heptane 82 Perfiuorotoluene 102 Perfluorocyclic ether (C l- 0) 101 Perfiuorocyclic ether (C F O) 56 Monochlotrotetrafiuoro-(trifluoromethyl) benzene--- 137 Dichlorotrifiuoro-(tnifiuoro-methyl) benzene Trichlorodifiuoro-(trifiuoromethyl) benzene 207 Monochloropentadecafluoroheptane 96 2-chloro-1,4-bis (trifluoromethyl) benzene 148 2-chlorotrifiuoromethylbenzene 150 Perfluorodiethylcyclohexane 148 Perfiuoroethylcyclohexane 101 Perfluoropropylcyolohexane 123 Chlorononafluorobis (trifluoromethyl) cyclohexane- 129 Perfluoronaphthalane 140 Perfluoro-l-methylnaphthalane 161 Perfluorodimethylnaphthalanes 177 to 179 Perfluoroindane 116 to 117 Perfiuorofiuorane 190 Perfluorobicyclo-(2.2.l) heptane (746 mm.) 70

The amines and ethers may have dissimilar halogen substituted hydrocarbon groups present as, for example, 2,2-dicl'rloro-1, 1 1-trifluoroethyl-perfluorobutyl ether and peiiluorodibutylethyl amine. The freezing points of the above-listed liquid compounds are below 0 C., many being below 5 0 C., so that they can be safely employed, individually or in mixtures, under nearly all ambient conditions to be expected in service.

Examples of preferred suitable fiuorinated compounds are the perfiuorocyclic ethers, such as the compound having the formula C F 0, although it will be understood that other fluorinated compounds as defined herein may be substituted in whole or in part therefor. The physical properties of the perfluorocycl ic ether (C F O) are as follows:

Boilingpoint, 101 C.

Heat of vaporization, 21 calories per gram at the boiling point.

Specific heat, 0.26 calories per gram.

Density, 1.76.

Freezing point, -100 C.

The heat of vaporization varies with the fluorinated compound being used and falls in the range of about 18 to 50 calories per gram.

Referring now to the drawing and FIG. 1 in particular, there is illustrated an electrical apparatus, more specifically a transformer 10 comprising a sealed casing or container 42 within which is disposed a. magnetic core structure 62 and electrical windings 112 associated therewith which are both supported on a suitable means such as the base member 94. The transformer 10 also includes the first and second auxiliary compartments or housings 20 and 30, respectively, which may each enclose any conventional type of circuit interrupting or switching means (not shown), such as tap-chang ng transfer or selector switches. For the purpose of simplifying the drawing, the bushings normally carried by the top or cover 96 of the casing 42 are not shown. The windings 112 are subjected to the flow of electrical current during service which develops heat in the core 62 and in the windings 112.

Referring to FIG. 3, the type of conventional circuit interrupting or switching means, such as tap-changing equipment, which may be disposed in the first and second auxiliary compartments or housings 20 and 30, respectively, is illustrated schematically. In this instance, the transformer is illustrated as comprising a first primary winding portion 110 having a fixed number of turns, a second primary winding portion 112 having a plurality of tap connections or leads 92 associated therewith and a secondary winding 120. A plurality of tap-changing selector switches 162 is disposed in the first auxiliary compartment 20 and connected in circuit relation with the tap connections or leads 92 of the winding portion 112. As best shown in FIG. 1, the tap connections or leads 92 enter the first auxiliary compartment 20 through the stationary contact or stud members 93 through the insulating panel or barrier member 22. A plurality of tap-changing transfer switches 152 is disposed in the second auxiliary compartment 30 and connected in circuit relation between the preventive auto-transformer or reactor 142 and the selector switches 162 in a conventional arrangement. During the operation of the tap-ch anging switches just described, the tap-changing transfer switches 152 are normally arranged to operate before the tap-changing selector switches 162 so that only the tap-changing transfer switches 152 actually intermpt arcs during operation. One end of the winding portion 110 may be connected to an alternating current circuit as indicated at terminal 122 while one end of the winding portion 112 may be connected to the same alternating current circuit at the terminal 124. The winding portion 110 is efiectivelly connected in series with a portion of the turns of the winding portion 112, as determined by the operation of the tapchanging switches 152 and 162, as is well known in the art. The secondary Winding 120 of the transformer 10 may be also connected to an alternating current circuit as indicated at the terminals 132 and 134. The transfer switches 152 may be connected in circuit relation with the selector switches 92 by the leads 95 which leave the first auxiliary compartment 20 through the stationary contact or stud members 91 and enter the second auxiliary compartment or housing 30 through the stationary contact or stud members 97 which pass through the insulating panel or barrier member 32 as best shown in FIG. 1.

The bottom of the casing 42 is formed to provide a sump 46 in which there is disposed a supply 44 of a fluorinated organic compound, such as perfluorocyclic ether. As illustrated, the supply of the fluorinated compound is so small that it does not come in contact with the core 62 or the winding 112 although it is to be understood that at least a small portion of the core 62 and the windings 112 may be immersed in a fluorinated compound in a particular application. In order to apply the liquid coolant 44 to the electrical windings 112, a pump 74 is disposed for operation to withdraw the liquid coolant 44 from the sump 46. The liquid coolant or compound passes from the pump 74 through a conduit 72 to a spray or flow device 64 for distributing or applying a spray or flow (not shown) of the fluorinated liquid compound over the core 62 and the windings 112.

The liquid fluorinated compound sprayed from the device 64 distributes itself as a thin film over the electrical windings 112 and the core 62 and is caused to evaporate freely if the core and windings or coils are hot, thereby absorbing heat from the core and coils proportional to the amount of the compound vaporized and its heat of vaporization. The evolved vapors of the fluorinated compound flow to the walls of the casing 42 where some condensation takes place. The condensate and any excess of liquid compound applied on the core and coils flow back into the sump 46 for recirculation by the pump 74. In a particular application, it may be necessary or advisable to employ a separate radiator or heat exchanger (not shown) if the walls of the casing 42 are not adequate to dissipate the developed heat to the atmosphere.

The casing 42 of the transformer 10 is initially charged with a quantity of a relatively inert gas, substantially non-condensable at moderate pressures and ordinary atmospheric temperatures such as those encountered over the normal operating temperature range of the transformer 10.. Examples of preferred suitable non-condensable gases include sulfur hexafluoride, perfiuoropropane (C 1 perfiuorocyclobutane (C Fe), and nitrogen or a mixture of two or more of these gases. Perfiuoropropane has a boiling point of approximately 37 C. and perfiuorocyclobutane has a boiling point of approximately 6 C. at atmospheric pressure. A charge of a suitable liquid fluorinated compound or liquid fluorocarbon such as perfluorocyclic ether, is then introduced into the casing 42. The non-condensable gas may be introduced into the casing 42 at substantially atmospheric pressure and atmospheric temperature. When the transformer is cold or inoperative, the liquid fluorinated compound will have only a small partial pressure due to the presence of a small amount of the vapors from the liquid compound. As the temperature of the core 62 and the windings 112 increases, the partial pressure of the vapors of the fluorinated compound will increase to thereby drive or push the non-condensable gas, such as sulfur hexafluoride, into the upper portion of the casing 42, since the density of a suitable non-condensable gas, such as sulfur hexafluoride, will be usually less than the density of the vapors of a suitable liquid fluorinated compound. In order to provide for the segregation or separation of the non-condensable gas from the vapors of the fluorinated compound in the casing 42 as the temperature of the windings 112 and the core 62 increases, a gas reservoir or auxiliary chamber (not shown) may be provided having a restricted gas passageway or conduit connected near the top or to the top portion 96 of the casing 42 in a particular application, as disclosed in US. Patents 2,858,355 and 2,759,987 and my copending application previously mentioned which are all assigned to the same assignee as the present application. It is to be understood that the same non-condensable gas should be employed in the first and second compartments 20 and 30, respectively, since during operation, even if different gases are provided initially in different parts of the over-all closed system, the gas will gradually intermix to provide the same blend of gases in all parts of the system.

As previously mentioned, the first and second auxiliary housings or chambers 20 and 30, respectively, are closely connected to or mounted on the main casing 42 of the transformer 10 as best shown in FIG. 1. In particular, the first auxiliary housing 20, in which the tap-changing selector switches 162 shown schematically in FIG. 3 may be disposed, includes a side wall portion 21 which is secured to the side wall portion of the main casing 42 by any suitable fastening means such as welding or bolts. The first auxiliary housing 20 also includes a throat portion 25 which extends from the side wall portion 21 of the first auxiliary housing 20 into the main casing 42 of the transformer 10 and includes a flanged portion 27 at one end thereof on which the insulating panel or barrier member 22 is disposed or secured by suitable means, such as bolts. It is to be noted that the throat portion 25 of the first auxiliary housing 20 provides a passageway through which the electrical connections (not shown) from the stationary contact or stud members 91 and 93 may enter the first auxiliary housing 20. The first auxiliary housing 20 also includes an outer opening 24 to permit access to the circuit interrupting or switching means which is disposed therein. The opening 24 is normally closed by a suitable cover or door member 26 which may be removably secured to the first auxiliary housing 20 by suitable means such as bolts (not shown).

Similarly, the second auxiliary housing or chamber 30 includes a side wall portion 31 that is secured to the side wall portion of the main casing 42 by suitable means (not shown), such as welding or bolts. The second auxiliary housing 30 also includes a throat portion 35 which extends from the side wall portion 31 of said auxiliary housing into the main casing 42 of the transformer and a flanged member 37 is provided at one end of said throat member to support the insulating panel or barrier member 32 by suitable means (not shown), such as bolts. In addition, the second auxiliary housing 30 similarly includes an opening 34 to permit access to the tap-changing switches 152 which are disposed therein, said opening being normally closed by a cover or door member36 which is removably secured to said auxiliary housing by suitable means (not shown) such as bolts. The throat portion 35 of the second auxiliary housing 30 also provides a passageway through which the electrical connections (not shown) to the stationary contact or stud members 97 mounted on the insulating barrier 32 may pass into the second auxiliary housing.

' In order to provide a suitable insulating or dielectric medium in the first auxiliary housing 20, the first auxiliary housing 20 is initially charged with a quantity of a relatively inert insulating gas which is substantially noncondensable at the pressures and temperatures encountered in the normal operating range of the transformer 10, such as sulfur hexafluoride. Since are products do not normally result during the operation of the tap-changing selector switches 162 which are disposed in the first auxiliary housing 20, it is not necessary that the insulating panel or barrier member 22 maintain a gastight separation between the first auxiliary housing 20 and the interior of the main casing 42 of the transformer 10. In order to provide a return path for any of the vapors of the fiuorinated compound 44 which may enter the first auxiliary housing 20 and then are condensed, the conduit 28 is provided which connects the lower end of the first auxiliary housing 20 to the interior of the main casing 42 of the transformer 10. Since the conduit 28 also operates as a gas passageway to maintain the first auxiliary housing 20 in gaseous communication with the interior of the main casing 42 of the transformer 10, the pressure of the non-condensable gas 38 which is disposed in said auxiliary housing is substantially the same as the pressure of the insulating gas inside the casing 42 which comprises a mixture of the vapors of the fiuorinated compound 44 and the non-condensable gas, such as sulfur hexafluoride which is also disposed in the casing 42.

Similarly, the second auxiliary housing 30, in which is disposed the tap-changing transfer switches 152 as previously described, is initially charged also with a quantity of a relatively inert insulating gas which is substantially non-condensable at the pressures and temperatures encountered over the normal operating range of the transformer 10 and which has suitable electronegative properties to provide an arc extinguishing medium in the second auxiliary housing 30. The non-condensable gas 38 which is disposed in the second auxiliary housing 34 is preferably sulfur hexafluoride in order to provide an improved arc extinguishing medium. In order to eliminate the need for a gastight or hermetic separation between the first auxiliary housing 30 and the main casing 42 of the transformer 10, the second auxiliary housing 30 is maintained in gaseous communication with the interior of the main casing 42 by the gas passageway or conduit 58 which connects the lower end of the second auxiliary housing 30 to the interior of the casing 42. The gas passageway 58 includes means for removing the are products which result from the operation of the tapchanging transfer switches 152 in the presence of sulfur hexafluoride to prevent arc products from entering and contaminating the insulating gas inside the main casing 42 of the transformer 10 which includes the vapors of the fiuorinated compound 44.

In particular, the means for removing or absorbing the are products of sulfur hexafluoride, more specifically the gas scrubber or cleaner, includes a housing or container 56 which is serially connected with the conduit 58 and in which is disposed a quantity of a suitable material for absorbing the arc products of sulfur hexafluoride, preferably activated alumina or soda-lime or mixtures of said absorbing materials. The latter absorbing material 54 may be supported in the container 56 by a suitable screen or sieve which serves to support the absorbmaterial but still permits the passage of gas therethrough into the conduit 82, which, in this instance, connects the container 56 with the interior of the main casing 42 of the transformer 10. It is to be understood that in certain applications the means for removing the are products of the sulfur hexafiuoride may be disposed in a container which provides a gas passageway directly through an opening in the side wall portions of the auxiliary housing 30 and the main casing 42 of the transformer 10, rather than having a separate conduit arrangement as illustrated in FIG. 1.

In order to provide a return path for the vapors of the fiuorinated compound '44 which may enter the auxiliary housing 30 and are then condensed, the conduit 98 is provided which connects the lower portion of the auxiliary housing 30 with the interior of the main casing 42 of the transformer 10. The conduit 98 is U-shaped so as to provide a liquid trap therein and thus prevent the vapors of the fiuorinated compound 44 which are disposed in the main casing 42 from entering the auxiliary housing 30 through the conduit 98. It is to be noted that the end of the conduit 98 which is disposed inside the main casing 42 of the transformer 10 must be disposed at a lower elevation than the end of the conduit 98 which is connected to the lower end of the auxiliary housing 30 in order to return the condensed vapors of the fiuorinated compound 44 to the interior of the casing 42.

In summary, the first and second auxiliary housings 20 and 30, respectively, need not be separated from the main casing 42 of the transformer 10 in a gastight arrangement since both of said auxiliary housings are maintained in gaseous communication with the interior of the main casing 42 of the transformer 10. The pressure of the non-condensable gas in the auxiliary housing 20 and the pressure of the non-condensable gas or sulfur hexafluoride in the auxiliary housing 30 are both substantially the same as the pressure of the insulating gas in the main casing of the transformer 10 as previously mentioned.

Referring to FIG. 2 of the drawings, there is illu trated another embodiment of the invention. In general, the transformer 210 is similar to the transformer 10 except that additional means are provided to permit replacing the absorbing material which removes the are products of the sulfur hexafiuoride and to permit the opening of the first and second auxiliary housings without opening the main casing of the transformer 210 to atmospheric pressure.

In particular, the transformer 210 includes a main casing 242 in which is provide a magnetic core 262 on which is disposed electrical windings 212 similarly to the transformer 10. The casing 242 includes a sump 246 in which is disposed a quantity of a fiuorinated compound 244 which may be applied to the magnetic core 262 and the windings 212 by any suitable means as previously described for the transformer 10. The transformer 210 also includes the first and second auxiliary housings 220 and 230, respectively, which are closely connected to or mounted on the main casing 242 of the transformer 210.

The first auxiliary housing 220 includes a removable cover 226, a throat portion 225 having a flanged member 227 at one end thereof which supports the insulating panel or barrier member 222. Similarly, the second auxiliary housing 230 includes a removable cover 236 and a throat portion 235 having a flange member 237 at one end thereof which supports the insulating panel or barrier member 232.

In order to permit removing of the cover member 226 of the first auxiliary housing 220 without exposing the interior of the main casing 242 of the transformer 210 to atmospheric conditions, the return conduit 228 from the first auxiliary housing 220 to the interior of the main casing 242 of the transformer 210 includes a valve 257 which may be closed before the cover 226 is removed from the first auxiliary housing 220, to thereby isolate the main casing 242 of the transformer 210.

"In order to isolate the main casing 242 of the transformer 210 and to prevent said main casing from being exposed to atmospheric conditions whenever the removable cover 236 is opened on the second auxiliary housing 230, the return conduit or liquid trap 298 includes a valve 255 while the conduit 253 which connects the second auxiliary housing 230 to the means for removing the are products of the sulfur hexafluoride includes the valve 253. The valves 253 and 255 are both closed before the removable cover 236 is opened on the second auxiliary housing 230.

In order to permit replacing the absorbing material 254 in the container 256 which is serially connected between the conduit 258 and the conduit 282 which leads to the interior of the main casing 242 of the transformer 210, the flange connections 2'61 and 284 are provided on the opposite sides of the container 256, while an additional valve 286 is provided in the conduit 282. Whenever the absorbing material 254 is to be replaced or renewed in the container 256, the valves 253 and 286 are first closed to prevent exposing the interiors of the second auxiliary housing 230 and the main casing 242 of the transformer 210 to atmospheric conditions. The flange connections 261 and 284 are then opened by suitable means such as removing bolts (not shown), and the absorbing material 254 may then be replaced. It is to be noted that the container 256 may also include a supporting screen or sieve 278 similarly to the container 56 of the transformer previously described.

Referring to FIG. 4, an alternate arrangement is illustrated, in a transformer 10 which is preferable when a high degree of segregation exists in the casing 42' with the non-condensable gas concentrated in the upper por. tion of said casing and the vapors of the liquid coolant concentrated in the lower portion of said casing. The arrangement is similar to that shown in FIG. 1 except 'that the ends of the gas passageways 28B and 82' connecting the first and second compartments 2G and 30', respectively, are terminated in the upper portion of the casing 42 in order to maintain as high as possible a concentartion of the non-condensable gas in both auxiliary compartments. The return conduits 28A and 98' may then be U-shaped to form liquid traps for returning to the casing 42' any of the liquid coolant which enters said compartments in the vapor state and is then condensed. In other words, the gas passageways connecting the casing 42' with the compartments 20 and 30 should be terminated in the portion of said casing or the closed system in which the highest concentration of the non-condensable gas exists whenever a high degree of gas-vapor segregation exists. It is to be noted that an alternate location of the housing 56 between the housing 42 and the compartment 30 is shown in FIG. 4 along with the necessary conduit connections and the original location of the housing 56" in phantom.

It is to be understood that in certain applications absorbing or scrubbing materials other than activated alumina or soda-lime may be employed which have a chemical aflinity for the are products of whatever noncondensable gas is employed as an arc extinguishing medium in the second auxiliary compartment 30. It is also to be understood that the teachings of the invention may be employed where other types of circuit interrupting 10 or switching means are disposed in the auxiliary compartments in a transformer of the type described.

The apparatus embodying the teachings of the invention has several advantages. For example, the construction disclosed for an electrical apparatus, such as a transformer, makes it unnecessary to maintain a gastight separation between a housing or compartment in which is disposed circuit interrupting or switching means associated with an electrical apparatus, such as a transformer. In addition the pressure of the insulating or are extinguishing gaseous medium provided in the auxiliary compartments connected to the main casing of an electrical apparatus is maintained at substantially the same value as the pressure of the insulating gas in said main casing without permitting the are products produced by the operation of circuit interrupting or switching means from entering said main casing and contaminating the insulating gas.

Since numerous changes may be made in the abovedescribed apparatus and different embodiments of the invention may be made without departing from the spirit and scope thereof, it is intended that all the matter contained in the foregoing description or shown in the accompanying drawing shall be interpreted as illustrative and not in a limiting sense.

I claim as my invention:

1. A transformer comprising a closed container, a winding disposed in said container which heats up during operation of said transformer, means for cooling said transformer comprising a fluorinated liquid compound which boils at a temperature between 50 C. and 225 C. at atmospheric pressure and means for distributing said com-pound over said winding to cool it mainly by evaporation of said compound, an auxiliary chamber disposed adjacent to said container, switching means disposed in said chamber and connected in circuit relation with said winding, a gas which is substantially non-condensable over the normal operating range of said transformer disposed in said container and in said chamber, an insulating gas in said container comprising a mixture of said non-condensable gas and the vapors of said compound, said non-condensable gas being adapted to aid in are extinction during the operation of said switching means, and means for cleaning said insulating gas interconnected between said container and said chamber to permit the passage of said insulating gas therethrough and to prevent are products from said chamber from entering said container.

2. A transformer comprising a closed container, a winding disposed in said container which heats up during operation of said transformer, means for cooling said transformer comprising a fluorinated liquid compound which boils at a temperature 'between 50 C. and 225 C. at atmospheric pressure and means for distributing said compound over said winding to cool it mainly by evaporation of said compound, an auxiliary chamber disposed adjacent to said container, switching means disposed in said chamber and connected in circuit relation with said winding, a gas which is substantially non-condensable over the normal operating range of said transformer disposed in said container and in said chamber, an insulating gas in said container comprising a mixture of said noncondensable gas and the vapors of said compound, said non-condensab-le gas being adapted to aid in arc extinction during the operation of said switching means, and means for cleaning said insulating gas interconnected between said container and said chamber to permit the passage of said insulating gas therethrough and to prevent are products from said chamber from entering said container, said non-condensable gas comprising sulfur hexafiuoride.

3. A transformer comprising a closed container, a winding disposed in said container which heats up during operation of said transformer, means for cooling said transformer comprising a fluorinated liquid compound which "boils at a temperature between 50 C. and 225 C.

at atmospheric pressure and means for distributing said compound over said Winding to cool it mainly by evaporation of said compound, an auxiliary chamber disposed adjacent to said container, switching means disposed in said chamber and connected in circuit relation with said winding, a gas which is substantially non-condensable over the normal operating range of said transformer disposed in said container and in said chamber, an insulating gas in said container comprising a mixture of said non-condensable gas and the vapors of said compound, said non-condensable gas being adapted to aid in are extinction during the operation of said switching means, and a gas passageway for connecting said container and said chamber, and means associated with said gas passageway for removing the are products from the insulating gas which passes therethrough.

4. A transformer comprising a closed container, a Winding disposed in said container which heats up during operation of said transformer, means for cooling said transformer comprising a fluorinated liquid compound which boils at a temperature between 50 C. and 225 C. at atmospheric pressure and means for distributing said compound over said winding to cool it mainly by evaporation of said compound, an auxiliary chamber disposed adjacent to said container, switching means disposed in said chamber and connected in circuit relation with said winding, a gas which is substantially non-condensable over the normal operating range of said transformer disposed in said container and in said chamber, an insulating gas in said container comprising a mixture of said non-condensable gas and the vapors of said compound, said non-condensable gas being adapted to aid in arc extinction during the operation of said switching means, and a gas passageway for connecting said container and said chamber, and means associated with said gas passageway for removing the are products from the insulating gas which passes therethrough, said non-condensable gas comprising sulfur hexafiuoride.

5. An electrical apparatus comprising an enclosing casing, an electrical winding disposed therein which heats up during its operation, means for dissipating the heat from said winding comprising a supply of fluorinated liquid coolant and means for applying a layer of said coolant over said winding to cool it mainly by evaporation of said coolant to a condensable vapor, the compound having a boiling point of between 50 C. and 225 C. at atmospheric pressure, an auxiliary housing secured to said casing, circuit interrupting means connected in circuit relation with said winding, said interrupting means being disposed in said auxiliary housing, a gas which is substant ally non-condensable over the normal operating range of said apparatus disposed in said casing and in said auxiliary housing to aid in arc extinction during the operation of said interrupting means, a dielectric medium in said casing comprising a mixture of the vapors of said fluorinated compound and said non-condensable gas, said dielectric medium predominantly comprising said non-condensable gas when said apparatus is cold and increasingly of the vapors of said fluorinated compound as said apparatus heats up, and a gas passageway connected between said casing and said housing to form a closed system, said passageway including means for absorbing the are products produced by the operating of said interrupting means.

6. An electrical apparatus comprising an enclosing casing, an electrical winding disposed therein which heats up during its operation, means for dissipating the heat from said winding comprising a supply of fluorinated liquid coolant and means for applying a layer of said coolant over said winding to cool it mainly by evaporation of said coolant to a condensable vapor, the compound having a boiling point of between 50 C. and 225 C. at atmospheric pressure, an auxiliary housing secured to said casing, circuit interrupting means connected in circuit relation with said winding, said interrupting means being disposed in said auxiliary housing, a gas which is substantially non-condensable over the normal operating range of said apparatus disposed in said casing and in said auxiliary housing to said in arc extinction during the operation of said interrupting means, a dielectric medium in said casing comprising a mixture of the vapors of said fluorinated compound and said non-condensable gas, said dielectric medium predominantly comprising said non-condensable gas when said apparatus is cold and increasingly of the vapors of said fluorinated compound as said apparatus heats up, and a gas passageway connected between said casing and said housing to form a closed system, said passageway including means for absorbing the arc products produced by the operating of said interrupting means, said non-condensable gas comprising sulfur hexafluoride.

7. An electrical apparatus comprising an enclosing container, a source of heat disposed in said container, means for dissipating the heat from said source comprising a fluorinated liquid compound and means for applying a layer of said compound over said source to cool it mainly by evaporation of the liquid compound, an auxiliary housing disposed adjacent to said container, circuit interrupting means disposed in said housing and operatively associated with said source of heat, a gas which is substantially non-condensable over the normal operating range of said apparatus disposed in said casing and in said housing, an insulating gas disposed in said casing comprising a mixture of the vapors of the fluorinated compound and said non-condensable gas, said non-condensable gas in said housing being adapted to aid in the extinction of arcs during the operation of said interrupting means, and a gas passageway interconnecting said casing and said housing to permit the passage of said insulating gas therebetween, said passageway including means for removing the are products from the gas which flows therethrough.

8. An electrical apparatus comprising an enclosing container, a source of heat disposed in said container, means for dissipating the heat from said source comprising a fluorinated liquid compound and means for applying a layer of said compound over said source to cool it mainly by evaporation of the liquid compound, an auxiliary housing disposed adjacent to said container, circuit interrupting means disposed in said housing and operatively associated with said source of heat, a gas which is substantially non-condensable over the normal operating range of said apparatus disposed in said casing and in said housing, an insulating gas disposed in said casing comprising a mixture of the vapors of the fluorinated compound and said non-condensable gas, said non-condensable gas in said housing being adapted to aid in the extinction of arcs during the operation of said interrupting means, a gas passageway interconnecting said casing and said housing to permit the passage of said insulating gas therebetween, said passageway including means for removing the are products from the gas which flows therethrough, and means interconnecting said casing and said housing for returning the condensed vapors of said com pound from said housing to said casing.

9. An electrical apparatus comprising an enclosing container, a source of heat disposed in said container, means for dissipating the heat from said source comprising a. fluorinated liquid compound and means for applying a layer of said compound over said source to cool it mainly by evaporation of the liquid compound, an auxiliary housing disposed adjacent to said container, circuit interrupting means disposed in said housing and operatively associated with said source of heat, a gas which is substantially non-condensable over the normal operating range of said apparatus disposed in said casing and in said housing, an insulating gas disposed in said casing comprising a mixture of the vapors of the fluorinated compound and said non-condensable gas, said non-condensable gas in said housing being adapted to aid in the extinction of arcs during the operation of said interrupting means, and a gas passageway interconnecting said casing and said housing 13 to permit the passage of said insulating gas therebetween, said passageway including means for removing the arc products from the gas which flows therethrough, said non-condensable gas comprising sulfur hexafluoride.

10. An electrical apparatus comprising an enclosing container, a source of heat disposed in said container, means for dissipating the heat from said source comprising a fluorinated liquid compound and means for applying a layer of said compound over said source to cool it mainly by evaporation of the liquid compound, an auxiliary housing disposed adjacent to said container, circuit interrupting means disposed in said housing and operatively associated with said source of heat, a gas which is substantially non-condensable over the normal operating range of said apparatus disposed in said casing and in said housing, an insulating gas disposed in said casing comprising a mixture of the vapors of the fluorinated compound and said non-condensable gas, said non-condensable gas in said housing being adapted to aid in the extinction of arcs during the operation of said interrupting means, and a gas passageway interconnecting said casing and said housing to permit the passage of said insulating gas therebetween, said passageway including means for removing the are products from the gas which flows therethrough, said gas passageway being disposed externally of said casing and said housing to permit replacing said removing means.

References ited in the file of this patent UNITED STATES PATENTS 

